We are looking at a new rule to simulate the effect on troops if no retreat is available. Although you could include this rule as an “always on” type of rule, we really are intending it mainly for battles where desperate defenses were a critical part of the battle. For instance, elements of Lee’s army at Antietam if backed up against the Potomac. Like any Pub Battles rule, the intent is to have as simple a rule as possible that retains authenticity and the feel of command.
A block that has no legal retreat is considered Desperate and ignores a treat result.
That is the whole rule, but just to make sure you can wrap your head around it, this is what it means:
The retreat is still counted, a fresh unit would still require 3 hits to be eliminated, but if a final result requires a retreat, it is simply ignored.
Note that it still counts the retreat, it just doesn’t actually retreat. So a Militia unit that takes a hit would flip to spent, but ignore the retreat requirement. Artillery can cause a unit to become spent, but not force it to retreat.
Let me know if you find something unclear about the rule. It seems pretty clear to me, but so does every rule written, to its author. It often depends on underlying assumptions that are impossible to anticipate.